Anatomía comparada del tallo y de la raíz de las especies del género Neoevansia Marshall (Cactaceae)

Anatomical characters of Neoevansia species were studied to gain insight in their contribution to the systematics of the genus. Characters of the dermal, fundamental, and vascular systems of the stem and root were evaluated and compared with severl species of Peniocereus, Wilcoxia, and Echinocereus. The results revealed that N. striata is characterized by a noncollenchymatous unistratified hypodermis and alternate intervascular pits in vessel elements in the secondary xylem; while N. lazaro-cardenasii and N. zopilotensis can be distinguished by their epidermic cell size and hypodermis width. The increment in volume in Neoevansia tuberous roots is mainly related to cell divisions in rays. Neoevansia lazaro-cardenasii, N. zopilotensis, and N. striata share with Peniocereus the fibrous wood and the phloem fiber cap. The results support the proposals of several authors to transfer the species of Neoevansia to the genus Peniocereus